JP2001032251A - Crack surveying device for bed rock - Google Patents

Abstract

PROBLEM TO BE SOLVED: To specify the position of a crack or a fracture zone by boring holes at equal intervals in a hole of a bet rock, inserting a bored tube including a pore water pressure meter in each hole, injection pressurized water, and displaying the measurement result as a distribution chart on a personal computer via a data logger. SOLUTION: A bored tube 1 is formed by drilling holes 2 at equal intervals in a hollow cylinder body having a length longer than the depth of a boring hole 3 and an outside diameter smaller than its inside diameter and internally arranging pore water pressure meters 6 at equal intervals. The bored tube 1 is inserted into the boring hole 3 while frictional resistance due to unevenness and a bend of the hole is reduced by means of a centralizer 5. A water injection port 10 is arranged in the opening part of the boring hole 3 while the other part is sealed by a seal 11, and water is injected at a constant pressure by means of a water pressurizing device 14. After the water pressure and the water flow become a constant state, the measurement result of the pore water pressure meter 6 is inputted into a personal computer 9 via a cable 7 and a data logger 8 so as to be displayed as a distribution chart. Then, water permeability in each pore water pressure meter 6 is grasped for checking the position of a crack 13 or a fracture zone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting cracks in rock.

[0002]

2. Description of the Related Art Conventionally, at a rock drilling site or the like, in order to investigate in advance the existence of cracks and crushing zones in the borehole, water is injected from the opening of the borehole in which the opening is sealed, and the pressure and injection pressure at that time are used. There was a device to measure the amount of water.

[0003]

The conventional device for detecting cracks and crush zones by measuring the water injection pressure and the amount of water injected into the borehole can evaluate the water permeability of the entire borehole. There was a problem that the position of the shatter zone could not be specified.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide a rock crack exploration apparatus capable of measuring a crack in a borehole and a position of a crush zone.

[0005]

According to the present invention, as a means for solving the above-mentioned problems, perforated pipes provided with holes at equal intervals arranged in holes in rock, and equidistant holes in perforated pipes are provided. Provided is a crack exploration device that includes an installed pore water pressure gauge and a water injection pressurizing device that injects water into a hole in a rock, and that detects a crack in a rock from the water pressure distribution in the hole.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <a> Perforated pipe The perforated pipe 1 used in the present invention is a hollow cylindrical body having a length equal to or greater than the depth of a boring hole. Its outside diameter is smaller than the inside diameter of the borehole, and its inside diameter is larger than the outside diameter of the pore water pressure gauge 6 described later. It also has equally spaced holes 2 communicating with the interior of the tube.

<B> Centrizer A sled-shaped centrizer 5 is installed at the tip of a perforated pipe. When a perforated pipe is inserted into a borehole, frictional resistance due to unevenness and bending of the hole is reduced, and a smooth charging operation is enabled.

<C> Pore pressure gauge A pore pressure gauge 6 is installed at equal intervals in a perforated pipe. The pressure of water that has entered the pipe through the hole provided in the pipe can be measured for each installation location. Each pore water pressure gauge 6 is connected by a cable 7, and the measured water pressure is measured by an electric signal.
Pull out of the hole through.

<D> Water inlet The water inlet 10 is located at the opening of the borehole. It is a dedicated opening for injecting water into the hole. Openings other than the water inlet 10 are completely sealed before water injection.

<E> Water injection pressurization device The water injection pressurization device 14 is a device that pressurizes water with a pump. The device 14 is fixed to the water inlet 10 via a water pipe. The device 14 is connected to the personal computer 9. By operating the personal computer 9, the rotation of the pump is controlled, and an arbitrary injection pressure can be obtained.

<F> Data Logger and Personal Computer Signals from the pore pressure gauge are connected to a personal computer 9 via a data logger 8 installed outside the hole.

<G> Measurement operation (steady state) A water inlet 10 is installed at the opening of the borehole. The opening is completely sealed 11 except for the water inlet 10. Thereafter, water 12 is injected into the hole from the water inlet 10 at a constant pressure by a known method. After confirming that the water pressure and the flow rate are in a steady state, the measurement result by the pore water pressure gauge 6 is input to the personal computer 9 via the data logger 8. The measurement results are shown in a distribution chart on the personal computer 9, and the water permeability is grasped from the water pressure measurement results for each installation location of the pore water pressure gauge 6. In the distribution map, the position of the crack 13 or the crush zone can be specified in a section where the pore water pressure is low.

<H> Measuring work (unsteady state) Water is injected from the water inlet 10 using the water injection pressurizing device 14 in the same manner as described above. After increasing the water pressure in the hole to an arbitrary water pressure, the injection of water is stopped. The change over time of the value sent from the pore pressure gauge is recorded. After the pressurization is started, the time until each pore pressure gauge reacts and the gradient of the pressure rise is confirmed on the record, whereby the position of the crack or the crush zone can be specified.

<I> Measurement Example FIG. 2 shows a measurement example. There is no drop in water pressure below 25 m on the right. This suggests that a crack exists around 25 m.

[0015]

According to the present invention, the following effects can be obtained. <B> By measuring the water permeability from the water pressure at each installation location of the pore pressure gauge, and showing the measurement results in a distribution map, it is possible to confirm the presence of cracks and crush zones in the area where the measured values are low in the holes. . <B> Since the measured value of the pore water pressure for each location can be known, by expressing this as a ratio with the permeability in the healthy part, the permeability coefficient of each section in the borehole can be known. Therefore, even when a plurality of cracks or crush zones exist in the hole, the positions thereof can be confirmed.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a crack exploration device for rock mass according to the present invention.

FIG. 2 is a diagram showing measurement results.

Claims (1)

[Claims] 1. A perforated pipe provided with holes at equal intervals arranged in a hole in a rock, a pore water pressure gauge installed at equal intervals in the perforated pipe, a water injection pressurizing device for injecting water into a hole in the rock. A rock crack detection system that detects rock cracks from the water pressure distribution in the borehole.